The space agency said Wednesday that the voltage change was first discovered on Sunday, and engineers think it might be a "soft short." In a mission status report, NASA's Jet Propulsion Laboratory said a soft short is a leak through something that's partially conductive of electricity, rather than a "hard short" that's caused by one wire contacting another.

The six-wheeled, nuclear-powered rover halted work as a precaution. Engineers hope to resolve the problem over the next day or so, and resume science activities as early as this weekend.

So far, there's no sign that the problem is related to a computer reboot earlier this month that put Curiosity in safe mode.

Curiosity landed in a Martian crater in August 2012 and has spent the last several months driving toward its ultimate destination, Mount Sharp.

NASA said that the rover weathered an earlier soft short on its landing day. That problem was traced to the explosive-release devices used for deployments shortly before and after the landing. Soft shorts reduce the level of robustness for tolerating other shorts in the future, and they can indicate a potential problem in whichever component is the site of the short, NASA said.